This grant is requested to support a program in basic research aimed at elucidation at the molecular level of the properties, mode of functioning, and mechanisms of regulation of receptors for vasoactive peptide hormones. Kinin peptides, of which bradykinin is an important example, are exquisitely potent vasoactive agonists and are released extracellularly instantaneously following tissue trauma and injury from high molecular weight prohormones, kininogens, through the action of specific proteases, kallikreins. The pharmacological action of kinins, which include vasodilatation, increased vascular permeability, smooth muscle contraction, pain, and cell proliferation, and the mechanism of kinin release indicate that these peptides serve important roles in a number of pathophysiological and physiological processes such as inflammation and blood pressure regulation. In order to understand the normal and abnormal control of these important processes, it is absolutely crucial to understand at the molecular level the functional and structural characteristics of kinin receptors. To this end, we have developed a comprehensive research plan with four intimately linked major goals: 1) To understand the nature of the binding of kinin agonists and antagonists to kinin receptors. This goal may ultimately lead to the development of new routes of manipulating these receptors in vivo. 2) To understand how agonist binding to kinin receptors translates into a stimulation of various intracellular effector enzymes including phospholipases and tyrosine and serine/threonine protein kinases. 3) To understand the cellular mechanisms underlying regulation of kinin receptors which includes receptor internalization and possibly also receptor phosphorylation. 4) To understand the structural basis of kinin receptor function by studying the biochemical properties of kinin receptors through receptor purification and receptor cDNA cloning. The results obtained from this multi-faceted research program will increase our knowledge of the mechanisms involved in kinin actions and should further enhance our understanding of pathologies in which kinins serve a role such as acute and chronic inflammation and hypertension. Our results should also be of general importance in understanding regulation of the vasculature and cell growth since the cellular signaling pathways used by kinins are common to several other vasoactive and mitogenic agonists.